Читать книгу Industrial Environmental Management - Tapas K. Das - Страница 37

A critical element of an interim strategy is enhanced recovery. This can be approached from two directions: reuse of products and recycling of materials. Reuse of products includes return, reconditioning, and remanufacturing. The energy required for reuse and recycling is one of the key factors determining recoverability of a product. The closer the recovered product is to the form it needs to be in for recycling, the less energy is required to make that transformation. From the standpoint of economic development it is worth pointing out that the reconditioning or remanufacturing cycle is relatively less costly; it requires roughly half the energy and twice the labor per physical unit of output.

Recycling materials means closing the loop between the supply of post‐consumer waste and the demand for resources for production. Recycling of materials will be the business of the Zero Emissions engineer; reuse of products will also involve the Zero Emissions engineer, but it will have lots of front‐end work from another professional, the concurrent engineer. Concurrent engineering, which incorporates aspects of industrial engineering, product design, and product manufacturing, is an integrated approach that seeks to optimize materials, assembly, and factory operation. These engineers examine the broader context of a product, including technology for managing the environmental impacts of its transport, intended use, recyclability, and disposal, as well as the environmental consequences of the extraction of the raw material used in its production.

The ultimate fate of all materials is thus dissipation, being discarded, or recycling and recovery. With 94% of materials extracted from the environment being converted to wastes, current levels of recovery are clearly not sufficient. Recovery of materials from wastes will reduce the extent of resource extraction (but will not slow the speed of material flows through the economy). Aluminum and lead are two resources currently being heavily recycled, but evidence shows that there is potential for a lot more resources to be recovered from wastes.

Sherwood plots are diagrams that permit the graphic comparison of concentrations of materials in nature against their commodity cost. The sample plot in Figure 1.7 shows that the price for a commodity depends on its concentration in nature before extraction and refining. Figure 1.8 is a similar plot for metal price (2004) as a function of dilution (concentration) of metals in commercial ores; the relationship illustrates the concept that the more dilute a material is in its native ore, the more expensive it will be to purify into a commodity material (Johnson et al. 2007).

Together, the Sherwood plots demonstrate the recovery potential of materials. The elements plotted above the line in Figure 1.7 should be vigorously recycled because they are present in individual by‐products in relatively high concentrations. Lead, zinc, copper, nickel, mercury, arsenic, silver, selenium, antimony, and thallium are more economical to recover from waste than from nature. Extensive waste trading could significantly reduce the quantity of material requiring disposal because resource extraction uses from wastes, not virgin feedstocks (Allen and Behmanesh 1994).